import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int a=sc.nextInt(),b=sc.nextInt();
        while (sc.hasNext()){
            int c=a-1;
            System.out.println(func(b-c));
        }
    }

    public static int func(int n) {
        if(n<4){
            return n-1;
        }
        return func(n-1)+func(n-2);
    }
}
